Experimental Investigation of Silicon-Based Micro-Pulsating Heat Pipe for Cooling Electronics

Abstract

A simultaneous temperature measurement and flow visualization experiment was performed to investigate the thermal and flow behaviors of a silicon-based micro-pulsating heat pipe (micro-PHP) with trapezoidal microchannels with a hydraulic diameter of 352 μm. FC-72 and R113 were used as working fluids. Variations in temperature versus time at different locations of the micro-PHP under different power inputs and typical flow patterns in microchannels were recorded. The evaporator wall temperature, or the maximum localized temperature, of the micro-PHP at moderate filling ratios was measured and compared to those derived from the empty microdevice (0% filling ratio). Experimental results showed that a micro-PHP embedded in a semiconductor chip could significantly decrease the maximum localized temperature. At a power input of 6.3 W, reductions in the evaporator wall temperature of about 42.1°C (or 34.1%) and 41.9°C (or 33.9%) were obtained for the micro-PHP charged with R113 at filling ratios of 41 and 58%, respectively. When the micro-PHP charged with FC-72, a maximum power input of about 9.5 W associated with a heat flux up to 10.7 W/cm² was reached at a moderate rise in wall temperature of the evaporator. The visualization study demonstrated that the evaporation, adiabatic, and condensation sections of the micro-PHP were largely occupied by annular, slug, and slug–bubbly flows, respectively, at a steady state characterized by sustained self-exciting oscillations of working fluid. However, no local nucleate boiling was detected in the micro-PHP at the power input range, which was different from the results reported for traditional PHPs.

Keywords:

• micro-pulsating heat pipe
• silicon wafer
• nucleate boiling
• flow visualization
• electronic cooling

Acknowledgments

The authors acknowledge financial support from the National Natural Science Foundation of China (Nos. 50925624 and 51076060), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), and the Startup Foundation of Jiangsu University for Advanced Scholars (No. 11JDG080).